SAP HANA - VDM CDS Views vs BW Info Cubes

The Classic OLTP (ECC) to OLAP (BW) data flow scenario:

Transfer structures, transfer rules, and update rules are legacy 3.x data flow components in SAP Business Warehouse (BW) used to map, transform, and load data from a source system into persistent data targets. SAP NetWeaver 7.0 and Later) uses Transformations method that replaced both transfer rules and update rules as of SAP NetWeaver 7.0. 

Extraction from ECC (OLTP)

ECC Extractors: Business content or custom extractors (such as function modules, views, or tables) gather operational data in ECC.
Delta Mechanisms: Updates use timestamps, delta queues, or numeric pointers to pull only changed records during scheduled runs.

Staging and Processing in BW (OLAP)

PSA (Persistent Staging Area): Acts as the first flat-structure receiving table in SAP BW where raw data lands unmodified from ECC.
Transformations & DTPs: Data Transfer Processes (DTP) move data out of the PSA, applying clean-up rules and logic defined in transformations.
DataStore Objects (DSOs): Standard or write-optimized DSOs serve as clean repository layers for consolidated records before they feed reporting cubes.

SAP Virtual Data Model (VDM) built on Core Data Services (CDS) views enables real-time, online operational reporting directly on live transactional data. Because it functions entirely as a virtual abstraction layer over the database, it eliminates data duplication, physical data loads, and reporting latency. This is significant advantage compared to the previous ECC (OLTP) to BW (OLAP) being the foundational architecture for SAP Enterprise Reporting.

  
SAP ABAP CDS Views (CDS) models and structures data using "Dimensions", specifically through analytical annotations that define master data and attributes. AND this is similar to the way Business Warehouse (BW) Info Cubes are structured; except that SAP Core Data Services (CDS) views do not store data physically while BEW InfoCubes stores data physically. 

SAP BW InfoCube Dimensions

1) Hard limit of 16: “There are 16 dimensions available in an Info Cube because the fact table can accommodate this number of dimensions in a star schema.”.
2) Pre-defined structure: Includes 3 system dimensions (Time, Unit, and Data Packet) and up to 13 user-defined dimension tables.
3) Characteristic limits: Each dimension can hold up to 248 characteristics due to database constraints.
4) Similarity: BW InfoCube & S/4 CDS are both data modeling tools.
5) Physical Data Store: is a persistent, physical multi-dimentsional data store in SAP Business Warehouse. The InfoCube storesdata in dedicated fact and dimension tabels (star schema).
6) OLTP to OLAP: Standard InfoCubes in SAP BW physically store data in tables and use scheduled data loads from OLTP database tables to OLAP infocube rather than live online access. As such, BW InfoCube is used in classic SAP BW for enterprise data warehousing, historical analysis, and heavy data aggregation.

SAP ABAP CDS Views (S/4HANA Analytics)

1) No rigid dimension count: CDS views use a flexible virtual data model (VDM) and associations rather than physical dimension tables.  
2) Flat or flexible modeling: Instead of grouping fields into rigid dimension buckets, a CDS view of type #CUBE can expose as many fields (attributes/characteristics) and measures as needed, linked dynamically via associations to separate #DIMENSION CDS views.
3) Field limits: Limited only by underlying SQL view and database column constraints (which allow hundreds of columns), rather than a strict 16-dimension container model. 
4) Similarity: BW InfoCube & S/4 CDS are both data modeling tools.
5) Virtual Data Model: it is code-based Virtual Data Model (VDM) defined in the ABAP/HANA layer. It is vitual and generally non-persistent and do not store any data (compared to BW cubes); they act as virtual data models that fetch, calculate, and structure data dynamically from underlying database tables at runtime.
6) On-line Real time: SAP S/4HANA Core Data Services (CDS) views operate directly on the underlying database without the need for traditional data staging. As such, SAP CDS is used heavily in SAP S/4HANA for Embedded Analytics and real-time operational reporting.

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